1. Field of the Invention
The present invention relates to a pattern antenna formed on a circuit board. The present invention relates particularly to a laminate pattern antenna that is compact and lightweight but that nevertheless permits wide-range transmission and reception, and to a wireless communication device equipped with such a laminate pattern antenna.
2. Description of the Prior Art
In mobile communication using compact wireless devices such as cellular phones or indoor wireless LAN (local area network) terminals, those wireless devices need to be equipped with compact, high-performance antennas. As compact antennas for such applications, slim planar antennas have been receiving much attention because they can be incorporated in devices. As planar antennas are used microstrip antennas, of which typical examples are short-circuiting microstrip antennas as shown in FIG. 20A and planar inverted-F antennas as shown in FIG. 20B. In recent years, as wireless devices are made increasingly compact, planar antennas obtained by further miniaturizing microstrip antennas as shown in FIG. 20A have been proposed, for example, in Japanese Patent Applications Laid-Open Nos. H5-347511 and 2000-59132.
Inverted-F-shaped wire-form antennas as shown in FIGS. 21A and 21B are also used. FIG. 21A is a top view of an inverted-F-shaped antenna 101 of which a grounding conductor portion 103 is connected to a grounding conductor plate 102. FIG. 21B is a sectional view of the inverted-F-shaped antenna 101, and shows that a current is fed to a feeder conductor portion 104 of the inverted-F-shaped antenna 101. However, as the graph shown in FIG. 22 indicates, an inverted-F-shaped antenna 101 like the one shown in FIGS. 21A and 21B is usable only in a narrow frequency range. FIG. 22 is a diagram showing the frequency response of the voltage standing wave ratio (VSWR) of the inverted-F-shaped antenna 101 shown in FIGS. 21A and 21B. A wire-form antenna obtained by making this type of antenna usable in a wider frequency range is proposed in Japanese Patent Application Laid-Open No. H6-69715.
As described above, the antennas proposed in Japanese Patent Applications Laid-Open Nos. H5-347511, 2000-59132, and H6-69715 are miniaturized as compared with common planar or linear (wire-form) antennas that have conventionally been used. However, any of these antennas is formed three-dimensionally on a circuit board, and thus requires a space dedicated thereto on the circuit board to which it is grounded. This sets a limit to the miniaturization of these types of antenna.
On the other hand, Japanese Patent Application Laid-Open No. H6-334421 proposes a wireless communication product that employs a circuit-board-mounted antenna such as an inverted-L-shaped printed pattern antenna. However, on its own, an inverted-L-shaped printed pattern antenna is usable only in a narrow frequency range as described above. According to another proposal, an inverted-L-shaped printed pattern antenna is used together with a microstrip-type planar antenna to make it usable in a wider frequency range. However, this requires an unduly large area to be secured for the antennas, and thus hinders their miniaturization.
An object of the present invention is to provide a laminate pattern antenna that is miniaturized by the use of a pattern antenna that is formed as a pattern on the surface or inside a circuit board, and to provide a wireless device equipped with such a laminate pattern antenna.
Another object of the present invention is to provide a laminate pattern antenna that is made usable in a wider frequency range by the use of a plurality of pattern antennas, and to provide a wireless device equipped with such a laminate pattern antenna.
To achieve the above objects, according to one aspect of the present invention, a laminate pattern antenna formed on a circuit board is provided with: a first antenna pattern formed as a driven element on a first surface of the circuit board; and a second antenna pattern formed as a passive element on a second surface of the circuit board.
According to another aspect of the present invention, a laminate pattern antenna formed on and in a multilayer circuit board is provided with: a plurality of first antenna patterns formed as a driven element on the surfaces of or at the interfaces between the layers constituting the circuit board; and a plurality of second antenna patterns formed as a passive element on the surfaces of or at the interfaces between the layers constituting the circuit board.
According to another aspect of the present invention, a wireless communication device is provided with: a laminate pattern antenna that permits at least either transmission or reception of a communication signal to or from an external device This laminate pattern antenna is provided with: a first antenna pattern formed as a driven element on a first surface of the circuit board; and a second antenna pattern formed as a passive element on a second surface of the circuit board.
According to another aspect of the present invention, a wireless communication device is provided with: a laminate pattern antenna that permits at least either transmission or reception of a communication signal to or from an external device. This laminate pattern antenna is provided with: a plurality of first antenna patterns formed as a driven element on the surfaces of or at the interfaces between the layers constituting the circuit board; and a plurality of second antenna patterns formed as a passive element on the surfaces of or at the interfaces between the layers constituting the circuit board.